The present invention concerns a detection gate for detecting substances, for example drugs, explosives, etc. The present invention also concerns a detection method implemented in such a detection gate.
A detection gate for detecting substances of the drugs, explosives, etc. type is generally installed in sensitive places (airports, railway stations, etc.) to detect whether individuals or objects (luggage) have been in contact with such substances.
A detection gate of the prior art is known that comprises a frame having two lateral uprights facing each other and which define between them a passage for an individual or an object, and a device for collecting substances transported by the ambient air that is located at the top of the two lateral uprights in order to connect them.
Each lateral upright comprises a plurality of air ejection nozzles, each being oriented towards the individual in the passage in order, when an individual passes through the gate, to eject air towards the said individual in order to detach and entrain the particles that are embedded in his garments.
The collection device comprises an introduction window that is situated above the passage.
The particles pulled away during the ejection of air are entrained towards the said introduction window and are thus conducted to a detector.
The detector is able to recognise, among the particles thus pulled away, particles of illicit substances, such as drugs, explosives, etc.
When the detector detects one of these particles, it emits an alarm signal in order to warn a person in the monitoring service so as to permit any actions for dealing with this alarm.
Such a detection gate is not entirely satisfactory since it is based on a principle of isolated collection of solid particles of the substances related to the isolated emission of air jets by the nozzles. However, the signal thus obtained, in an isolated manner, intended for the detector, may prove to be insufficient in certain operational situations. Individuals carrying substances to be detected may then defeat the detection gate.